Sodium heated helical coil arrangement

ABSTRACT

A superheater heated by liquid sodium which is efficient, occupies a minimum of space and provides means to safely exhaust the products of an accidental sodium-water reaction. Saturated steam flows through downcomers which pass between a tube bundle support pipe and a relief duct extending co-axially within the support pipe and then upwardly through helical coils which encircle the support pipe and which are heated by downward flowing liquid sodium.

United States Patent Polcer et al.

SODIUM HEATED HELICAL COIL ARRANGEMENT Inventors: John Polcer, Florham Park; Robert O. Barratt, Parsippany, both of NJ.; John Roberts, San Jose, Calif.

Assignees: Foster Wheeler Corporation,

Livingston, N.J.; General Electric Company, San Jose, Calif.

Filed: Mar. 8, 1971 Appl. No.: 121,665

U.S. Cl. 122/34, 122/483 Int. Cl. F22b 1/06 Field of Search 122/34, 32, 483; 165/142,

References Cited UNITED STATES PATENTS 6/1965 Ammon 122/32 X May 28, 1974 3,245,464 4/1966 Ammon ct al. 122/32 X 3,279,439 10/1966 Ammon, 122/483 X 3,395,676 8/1968 Sprugue 122/32 Primary Examiner-Kenneth W. Sprague Attorney, Agent, or Firm.lohn E. Wilson; Marvin A. Naigur 5 Claims, 1 Drawing Figure rmmwnm am 3812.825

as I 68 INVENTORS ROBERT O. BARRATT JOHN POLCER JOHN ROBERTS ATTORNEY SODIUM HEATED HELICAL COIL ARRANGEMENT BACKGROUND OF THE INVENTION In nuclear power plants it is necessary to superheat steam without undue risk of extensive damage caused by a sodium-water reaction in an apparatus which is reliable and which affords access for inspection and/or repair. One class of design contemplates bayonet tubes in which steam flows through the inner one of two axially positioned tubes and then the reverse direction between the two tubes. Because of the large temperature difference between the two streams of steam on opposite sides of the inner tube, it has been necessary to insulate the inner tube. The resulting complexity makes this design somewhat undesirable.

Another possibility is to use a helical coil tube superheater in a liquid sodium nuclear power plant. However. there are several problems concomitant with most helical coil arrangements. The coils must be supported against vibration and it is often a problem to provide for quick and safe exhaustion of the products of a sodium-water reaction occurring because of a tube failure.

SUMMARY OF THE INVENTION It is an object of the present invention to overcome drawbacks found in the prior art such as those discussed above. Accordingly, saturated steam is passed through downcomers which extend between a relief duct and a co-axial tube bundle support pipe which insulates it. The steam then passes upwardly through helical coils which are heated by sodium flowing downwardly over them.

BRIEF DESCRIPTION OF THE DRAWING The drawing is a front view partly in section of a superheater made in accordance with the present invention.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENT The present helical coil superheater indicated generally as has a cylindrical pressure vessel 12 which includes a main section 14 and a head section 16 which are generally circular in horizontal cross-section. At the lower end of the head section is an annular flange 18 which is secured on top of an annular flange 20 on the top of the main section 14. The head section 16 includes an inlet toroid 24 which is fed with steam through inlets 26. The inlet toroid 24 is defined by an outer vertical wall 28, and inner vertical wall 30 and an annular plate 32 which is bolted at its marginal portions to the tops of the vertical walls 28 and 30.

The steam flows from the inlet toroid 24 through downcomer tubes 36 which pass within'a tube bundle support pipe 38. The tube bundle support pipe 38 is outwardly flared at its upper end portion 40 so that it is wide enough at its upper end to accomodate all of the downcomer tubes 36.

The downcomer tubes 36 occupy an annular space between the tube bundle support pipe 38 and a central relief duct 42 which is positioned within and is co-axial with the tube bundle support pipe 38. The function of the central relief duct 42 will be explained in detail presently.

The tubes pass downwardly beyond the tube bundle support pipe 38 and the central relief duct 42 through an annular sheet 44 and are each joined to a connecting section 46 which extends outwardly and upwardly back through the annular sheet 44 and through an annular perforated plate 48 and an annular perforated bottom lateral support plate 50. Each of the connecting sections is joined to a helical section 52 (only several of which are shown for the sake of clarity), which carry the steam to an elevation slightly below distribution rings 54, the function of which will be explained presently. The helical tube sections are joined at their upper ends to upwardly extending riser sections 56 which lead to an annular tube sheet 60 which extends outwardly from the tube bundle support pipe 38. After exiting the riser section 56, the steam passes through collecting chambers 62 which cover portions of the sheet 60 and then leaves by the steam outlets 64.

The steam is superheated while in the helical sections 52 by downward flowing liquid sodium. The sodium enters the superheater 10 through sodium inlets 68. The sodium then passes to the annular space occupied by the straight riser sections 56 which extend between the distribution rings 54 and calming rings 70. The sodium is distributed by the rings 54 uniformily down over the straight sections 56, the helical sections 52 and through the annular bottom support member 50, the annular plate 48 over the sheet and through the hole in its center. The sodium then flows through an orifice 74 in a bottom plate 76. The sodium then flows through a sodium outlet 80 and is returned to the reactor for reheating.

The helical coil sections 52 are supported by a bracket 81. The bracket 81 consists of a collar encircling the tube support bundle 38 and a number of radially extending arms which are connected to the riser sections 56. Each arm can support a number of riser sections and thus support the helical sections joined to them.

The pressure vessel 10 is protected at its inside surface with a cladding of stainless steel. In the event that liquid sodium should impinge against the pressure vessel, the stainless steel will delay its burning through long enough for detection devices to indicate the presence of a sodium-water reaction and for corrective measures to be taken. Within and spaced from the pressure vessel 10 is a flow shroud 82 which extends outwardly into the sodium inlets 68 and above and below them adjacent to the inner walls of the pressure vessel. The flow shroud 82 is flared inwardly at its bottom portion 84 and engages at its end with a sleeve 86 which places the orifice 74 in direct communication with the sodium outlet 80. A stagnant layer of sodium will be trapped between the flow shroud 82 and the pressure vessel 10 to provide insulation. This stagnant sodium will not leak into the sodium outlet because the bottom of the sleeve 86 is fitted with a sealing ring 88 which engages against the inner surface of the sodium outlet 80. With this arrangement, the head portion 18 and the insides of the present superheater 10 can be lifted out of the pressure vessel main section 14 for inspection and/or repair without breaking any members at the lower seal between the flow shroud 84 and the pressure vessel 12. Similarly, the insides can be replaced by simply lowering them into the pressure vessel main portion 14 and the sealing ring will seal against the inner surface of the sodium outlet 80.

When sodium flows through sodium inlet 68, it will assume a level somewhat above the inlet in the annular space outside of the tube bundle support pipe 38. There will be an annular body of stagnant sodium between the tube bundle support pipe 38 and the central release duct 42. This is desirable because it prevents the straight downcomer sections of the tubes 36 from being exposed to an excessive amount of heat. Further, it will prevent damage to the central relief duct 42, which in the event of a sodium-water reaction will exhaust the products of that reaction upwardly through a sodium-water reaction vent 90. The sodium-water reaction vent 90 is flared outwardly at its bottom to accomodate a hood 92 which directs the products of the reaction into the sodium-water reaction vent 90. With the present arrangement, the products of the reaction will have a flow path of very little resistance and which is straight so that the products can be quickly exhausted without excessively damaging the present superheater l0.

The above describes but one preferred embodiment. Other embodiments are possible without exceeding the scope of the present invention as defined in the following claims.

What is claimed is:

l. A sodium heated superheater comprising a vertically elongated pressure vessel, a liquid sodium inlet in said pressure vessel, a sodium outlet adjacent to the bottom of said vessel, a tube bundle support pipe within and co-axial with said vessel, a sodium reaction relief duct open at both ends within and co-axial with said support pipe, a plurality of downcomer tubes extending down between and to an elevation below said support pipe and said relief duct, a plurality of helical coil sections below said liquid sodium inlet and above said sodium outlet, a plurality of tubular connecting sections,

each of said downcomer tubes joined to one of said tubular connecting section which connects each of said downcomer tubes with one of said helical coil sections, said helical coil sections extending upwardly between said support pipe and said vessel, whereby saturated steam passes down said downcomer tubes through said connecting sections and upwardly through said helical coil sections, and said sodium flows in through said sodium inlet and down over said coils to superheat said steam, said sodium filling the space between said relief duct and said support pipe to create a stagnant body of sodium having a level below the top of said relief pipe.

2. The superheater defined in claim 1 wherein said helical coil sections are supported by a bracket comprising a collar secured around said tube bundle support pipe and a plurality of arms extending radially from said collar, each of said arms supporting a plurality of helical coil tube sections.

3. The superheater defined in claim 2 wherein said arms are connected to said riser sections to thereby support said helical coil tube sections.

4. The superheater defined in claim 1 further comprising an annular sheet encircling said tube bundle support pipe above said sodium inlet, a plurality of said helical coils being connected with said sheet to direct steam through said sheet, a collecting chamber communicating with the top of said sheet, a steam outlet, said collecting chamber adapted to direct steam to said outlet.

5. The superheater defined in claim 2 wherein said pressure vessel comprises a main section and a head section secured to the top of said main section, said steam outlet being mounted in said head section. 

1. A sodium heated superheater comprising a vertically elongated pressure vessel, a liquid sodium inlet in said pressure vessel, a sodium outlet adjacent to the bottom of said vessel, a tube bundle support pipe within and co-axial with said vessel, a sodium reaction relief duct open at both ends within and co-axial with said support pipe, a plurality of downcomer tubes extending down between and to an elevation below said support pipe and said relief duct, a plurality of helical coil sections below said liquid sodium inlet and above said sodium outlet, a plurality of tubular connecting sections, each of said downcomer tubes joined to one of said tubular connecting section which connects each of said downcomer tubes with one of said helical coil sections, said helical coil sections extending upwardly between said support pipe and said vessel, whereby saturated steam passes down said downcomer tubes through said connecting sections and upwardly through said helical coil sections, and said sodium flows in through said sodium inlet and down over said coils to superheat said steam, said sodium filling the space between said relief duct and said support pipe to create a stagnant body of sodium having a level below the top of said relief pipe.
 2. The superheater defined in claim 1 wherein said helical coil sections are supported by a bracket comprising a collar secured around said tube bundle support pipe and a plurality of arms extending radially from said collar, each of said arms supporting a plurality of helical coil tube sections.
 3. The superheater defined in claim 2 wherein said arms are connected to said riser sections to thereby support said helical coil tube sections.
 4. The superheater defined in claim 1 further comprising an annular sheet encircling said tube bundle support pipe above said sodium inlet, a plurality of said helical coils being connected with said sheet to direct steam through said sheet, a collecting chamber communicating with the top of said sheet, a steam outlet, said collecting chamber adapted to direct steam to said outlet.
 5. The superheater defined in claim 2 wherein said pressure vessel comprises a main section and a head section secured to the top of said main section, said steam outlet being mounted in said head section. 